This invention relates to polyvinyl chloride moldable compositions used in producing flexible unitary shoe soles. More particularly, it covers a polyvinyl chloride composition in which a cellulose fibrous flock has been incorporated therein to form a thermoplastic compounded molding material which, when molded into a shoe sole product, produces a shoe sole that has improved flex life, is light in weight, and has the dull appearance of crepe rubber. This dull appearance is highly desirable from a consumer acceptance standpoint since it is associated with the skid resistance and oil resistance of synthetic rubbers. Shiny soles on the other hand are thought by consumers to have just the opposite properties.
It is well known in the art that leather shoe soles have a high rate of deterioration because of the constant wetting and drying that soles are subjected to during wear. To avoid this deterioration, many synthetic plastic materials have been introduced and used to form shoe sole compositions, such as vulcanized vinyl aromatic polymers having filler and cellulose flock therein to simulate a leather shoe sole. Shoe sole compositions using a rubber base are disclosed in the U.S. patents to Gates U.S. Pat. Nos. 2,638,457 and to Guinzburg 2,039,529. These patents cover rubber products having dispersed therethrough textile fibers as fine as flock useful for forming thin sheets of rubber in vulcanized form from which shoe soles can be made. Also, the U.S. patent to Himes U.S. Pat. No. 4,133,795 is directed to compositions for forming a shoe sole that simulates crepe rubber by forming a melt blend of monoalkenyl arene/diene block copolymers, crystal grade polystyrene, a hydrocarbon extending oil, and finely divided synthetic fibers.
The U.S. patent to Lonning U.S. Pat. No. 3,959,895 covers a molded unitary shoe sole from a fused admixture of a polyvinyl chloride polymer and a two stage core grafted composite copolymer having a particular butadiene-styrene rubbery substrate.
It is also known in the art to use a vulcanizable polyvinyl chloride molding compound containing inorganic fillers for use in producing shoe soles, but such compositions do not have the crepe-like appearance of rubber or the lightness in weight which is important in consumer acceptance of unitary shoe sole products. Also, this type of product is devoid of ease of flexing and presents a shiny plastic-like appearance which is detrimental to its use as a unitary shoe soling material where the sole per se and the heel are molded in one piece.